It just says the four internet audio file providers. I have no idea what it means by providers though.

It also says things about approved and non-approved file formats - again, no idea which is which, or even who approves them.

I've sent an email to my lecturer about it, but haven't heard anything rom him in a few days...

Oh, and AIFF was developed by apple in 1988 based on IFF files by EAAAC is a lossy compressed format similar to mp3 - developed by Sony and Nokia, among others

It's the word providers that gets it for me. I'd say you're looking for streaming sites or sites where you can purchase downloadable audio. With the approved/non-approved bit I'd say that mp3 is more common to get downloads in as it's probably the most common format out there, also you'd mention AAC, FLAC, m4a and other less common types, the non-approved ones would probably be wav as they're so huge in file-size that an album would be ridiculously large. Simple samples would be acceptable in wav though.